Project description:Regulation of the stability of epigenetic regulators offers unique opportunities for epigenetic therapies. However, this strategy has been poorly explored. Here we report that the E3 ubiquitin ligase UBE3A binds and ubiquitylates the histone H3-lysine 4-methyltransferase MLL4 (aka KMT2D) as a new substrate for degradation. Using Ube3a knockout and UBE3A-overexpressing transgenic mouse models, we show that, in the liver, UBE3A levels are inversely correlated with levels of MLL4, its functional surrogate marker H3-lysine 4-monomethylation, and expression of the recently identified steatosis target genes of MLL4. Consistently, Ube3a knockout mice are highly susceptible to high-fat diet-induced steatosis relative to their littermate control mice, and this phenotype is rescued by deletion of a copy of Mll4. Therefore, UBE3A indirectly exerts an epigenetic gene regulation activity through targeting MLL4 for degradation. Also this UBE3A-MLL4 axis presents a novel therapeutic venue for treating various MLL4-directed pathogeneses.
Project description:Angelman syndrome (AS) is a neurogenetic developmental disorder that results from the loss of E3 ubiquitin ligase UBE3A due to mutations in or deletions of the maternally inherited UBE3A allele. While mouse models of AS have implicated abnormal synaptic signaling and plasticity underlying behavioral dysfunction, how the loss of UBE3A contributes to hyperactivity of neuronal networks seen in AS patients remains unclear. Here, by utilizing human induced neurons and 3D cortical organoids derived from AS patient iPSCs and CRISPR-Cas9 mediated UBE3A KO hESCs, we uncovered a novel role of UBE3A in suppressing neuronal hyperexcitability via ubiquitin-mediated degradation of BK channels. More importantly, augmented BK channel activity in neurons manifested as increased intrinsic excitability of neurons and network level bursting and synchronization, which can be pharmacologically normalized by BK antagonists. Our study has illustrated the utility of modeling neurological diseases with human neural cells, and our results have provided new insights into underlying pathophysiological mechanisms and potential therapeutic strategy in Angelman syndrome.
Project description:Angelman syndrome is caused by loss of funtional ubiquitin E3 ligase UBE3A and results in severe deley in cognitive and motor development. In neurons, UBE3A locates to the synapse and to the nucleus. Loss of nuclear UBE3A results in development of Angelman syndrome like symptoms in mice. UBE3A can function as transcriptional coactivator of steroid hormone receptors, but the entire function of UBE3A in the nucleus is still not clear. So we wanted to study differences in the transcriptome in neurons differentiated from iPSCs that were derived from patients with Angleman syndrome and normal controls.
Project description:Ubiquitin-protein ligase E3A (UBE3A) has dual functions as a E3 ubiquitin-protein ligase and coactivator of nuclear hormone receptors. Mutations or deletions of the maternally inherited UBE3A gene cause Angelman syndrome. Here, we performed transcriptome profiling in the hippocampus of Ube3am+/p+ and Ube3am-/p+ mice, and determined that the expression of the retinoic acid (RA) signalling pathway was downregulated in Ube3a-deficient mice compared to WT mice. Furthermore, we demonstrated that UBE3A directly interacts with RARα and may function as a coactivator of the nuclear receptor RARα to participate in the regulation of gene expression. Loss of UBE3A expression caused the downregulation of the expression of RA-related genes, including Erbb4, Dpysl3, Calb1, Pten and Arhgap5 in Ube3am-/p+ mice brain tissues. This work revealed a new role for UBE3A in regulating retinoic acid (RA) signalling downstream genes and hopefully to shed light on the potential drug target of AS.
Project description:Brassinosteroids (BRs) regulate plant growth, development and stress responses by activating the core transcription factor BRI1-EMS-SUPPRESSOR1 (BES1). The E3 Ubiquitin ligase(s) that modify BES1 for autophagy-mediated degradation remain to be fully defined. In this study, we identified an F-box family E3 ubiquitin ligase termed BES1-ASSOCIATED F-BOX1 (BAF1). BAF1 interacts with and ubiquitinates BES1. Accordingly, BES1 stability and protein levels were reduced in BAF1 overexpression plants but increased in a baf1 loss-of-function mutant and in BAF1-DF (BAF1 with F-box deleted, dominant-negative form) overexpression lines. Selective autophagy of BES1, but not bulk autophagy, was significantly compromised in the baf1 mutant under sucrose starvation. BES1 degradation mediated by BAF1 could be blocked through autophagy but not proteasome inhibitors, suggesting that BAF1 mediates BES1 degradation largely through autophagy. baf1 and BAF1-DF overexpression plants had increased BR-regulated growth but were sensitive to long-term sucrose starvation, while BAF1 overexpression plants had decreased BR-regulated growth but were highly tolerant of sucrose starvation. Our results not only established BAF1 as a novel E3 ubiquitin ligase that targets BES1 for degradation through selective autophagy pathway, but also revealed a mechanism for plants to reduce growth during sucrose starvation by targeting this central growth regulator.
Project description:UBE3A encodes a E3 ubiquitin ligase whose loss from the maternal allele causes the neurodevelopmental disorder Angelman syndrome. Previous studies of UBE3A function have not examined full Ube3a deletion in mouse, the complexity of imprinted gene networks in brain, nor the molecular basis of systems-level cognitive dysfunctions in Angelman syndrome. We therefore utilized a systems biology approach to elucidate how UBE3A loss impacts the early postnatal brain in a novel CRISPR/Cas9 engineered rat Angelman model of a complete Ube3a deletion. Strand-specific transcriptome analysis of offspring from maternally or paternally inherited Ube3a deletions revealed the expected parental expression patterns of Ube3a sense and antisense transcripts by postnatal day 2 (P2) in hypothalamus and day 9 (P9) in cortex, compared to wild-type littermates. The dependency of genome-wide effects on parent-of-origin, Ube3a genotype, and time (P2, P9) was investigated through transcriptome (RNA-seq of cortex and hypothalamus) and methylome (whole genome bisulfite sequencing of hypothalamus). Weighted gene co-expression and co-methylation network analyses identified co-regulated networks in maternally inherited Ube3a deletion offspring enriched in postnatal developmental processes including Wnt signaling, synaptic regulation, neuronal and glial functions, epigenetic regulation, ubiquitin, circadian entrainment, and splicing. Furthermore, we showed that loss of the paternal Ube3a antisense transcript resulted in both unique and overlapping dysregulated gene pathways with maternal loss, predominantly at the level of differential methylation. Together, these results provide a holistic examination of the molecular impacts of UBE3A loss in brain, supporting the existence of interactive epigenetic networks between maternal and paternal transcripts at the Ube3a locus.
Project description:PROteolysis Targeting Chimeras (PROTACs) are bifunctional molecules that degrade target proteins through recruiting E3 ligases. However, their application is limited in part because few E3 ligases can be recruited by known E3 ligase ligands. In this study, we identified piperlongumine (PL), a natural product, as a covalent E3 ligase recruiter, which induces CDK9 degradation when it is conjugated with SNS032, a CDK9 inhibitor. The lead conjugate 955 can potently degrade CDK9 in a ubiquitin-proteasome-dependent manner and is much more potent than SNS-032 against various tumor cells in vitro. Mechanistically, we identified KEAP1 as the E3 ligase recruited by 955 to degrade CDK9 through a TurboID-based proteomics study, which was further confirmed by KEAP1 knockout and the nanoBRET ternary complex formation assay. In addition, PL-Ceritinib conjugate can degrade EML4-ALK fusion oncoprotein, suggesting that PL may have a broader application as a covalent E3 ligase ligand in targeted protein degradation.
Project description:Angelman Syndrome (AS) is a severe neurodevelopmental disorder, caused by the neuronal absence of the ubiquitin protein ligase E3A (UBE3A). UBE3A promotes ubiquitin-mediated protein degradation and functions as a transcriptional coregulator of nuclear hormone receptors, including the glucocorticoid receptor (GR). Previous studies showed anxiety-like behavior and hippocampal-dependent memory disturbances in AS mouse models. Hippocampal GR is an important regulator of the stress response and memory formation, and we therefore investigated whether the absence of UBE3A in AS mice disrupted GR signaling in the hippocampus. We first established a strong cortisol-dependent interaction between the GR ligand binding domain and a UBE3A nuclear receptor box in a high-throughput interaction screen. In vivo, we found that UBE3A-deficient AS mice displayed significantly more variation in circulating corticosterone levels throughout the day compared to wildtypes (WT), with low to undetectable levels of corticosterone at the trough of the circadian cycle. Additionally, we observed an enhanced transcriptomic response in the AS hippocampus following acute corticosterone treatment. Surprisingly, chronic corticosterone treatment showed less contrast between AS and WT mice in the hippocampus and liver transcriptomic responses. This suggests that UBE3A limits the acute stimulation of GR signaling, likely as a member of the GR transcriptional complex. Altogether, these data indicate that AS mice are more sensitive to acute glucocorticoid exposure in the brain compared to WT mice. This suggests that stress responsiveness is altered in AS which could lead to anxiety symptoms.
Project description:The dysregulation of genes in neurodevelopmental disorders that lead to social and cognitive phenotypes is a complex, multilayered process involving both genetics and epigenetics. Parent-of-origin effects of deletion and duplication of the 15q11-q13 locus leading to Angelman, Prader-Willi, and Dup15q syndromes are due to imprinted genes, including UBE3A, which is maternally expressed exclusively in neurons. UBE3A encodes a ubiquitin E3 ligase protein with multiple downstream targets, including RING1B, which in turn monoubiquitinates histone variant H2A.Z. To understand the impact of neuronal UBE3A levels on epigenome-wide marks of DNA methylation, histone variant H2A.Z positioning, active H3K4me3 promoter marks, and gene expression, we took a multi-layered genomics approach. We performed an siRNA knockdown of UBE3A in two human neuroblastoma cell lines, including parental SH-SY5Y and the SH(15M) model of Dup15q. Genes differentially methylated across cells with differing UBE3A levels were enriched for functions in gene regulation, DNA binding, and brain morphology. Importantly, we found that altering UBE3A levels had a profound epigenetic effect on the methylation levels of up to half of known imprinted genes. Genes with differential H2A.Z peaks in SH(15M) compared to SH-SY5Y were enriched for ubiquitin and protease functions and associated with autism, hypoactivity, and energy expenditure. Together, these results support a genome-wide epigenetic consequence of altered UBE3A levels in neurons and suggest that UBE3A regulates an imprinted gene network involving DNA methylation patterning and H2A.Z deposition.
Project description:The E3 ubiquitin ligase Ube3a is biallelically expressed in mitotic cells, including neural progenitors and glial cells, raising the possibility that UBE3A gain-of-function mutations might cause neurodevelopmental disorders irrespective of parent-of-origin. To test this possibility, we engineered a mouse line that harbors an autism-linked UBE3A-T485A (T508A in mouse) gain-of-function mutation and evaluated phenotypes in animals that inherited the mutant allele paternally, maternally, or from both parents. We found that both paternally and maternally expressed UBE3A-T485A resulted in elevated UBE3A activity in neural progenitors and glial cells where Ube3a is biallelically expressed. Expression of UBE3A-T485A from the maternal allele, but not the paternal one, led to a persistent elevation of UBE3A activity in postmitotic neurons. Maternal, paternal, or biparental inheritance of the mutant allele promoted embryonic expansion of Zcchc12 lineage interneurons which mature into Sst and Calb2 expressing interneurons, and caused a spectrum of behavioral phenotypes that differed by parent-of-origin. Phenotypes were distinct from those observed in Angelman syndrome model mice that harbor a Ube3a maternal loss-of-function allele. Our study shows that the UBE3A-T485A gain-of-function mutation causes distinct neurodevelopmental phenotypes when inherited maternally or paternally. These findings have clinical implications for a growing number of disease-linked UBE3A gain-of-function mutations.